Wear resistant nonwoven fabric

ABSTRACT

NONWOVEN FABRIC MADE UP OF SUBSTANTIALLY CONTINUOUS FILAMENTS HAVING A RELATIVELY LOW DENIER AND IMPREGNATED WITH BINDER MATERIAL CONCENTRATED AT BOTH MAJOR SURFACES THEREOF. METHOD OF MAKING SUCH BONDED FABRIC BY INTRODUCING BINDER IN THE FORM OF A FOAM ONTO BOTH SURFACES OF A NONWOVEN FLEECE, PREFERABLY SEQUENTIALLY, AND DRYING SUCH BINDER IN A MANNER SUCH THAT THE BINDER PARTICLES TEND TO MIGRATE AND CONCENTRATE AT THE FABRIC SURFACE.

Aug. 29 1972 l.. HARTMANN 3,687,712

WEAR RESISTANT NoNwovRN FABRIC Filed April 1e, 1968 g. i" i:

INVENTOR 0R, UDM/1@ HARTMANN ATTORNEYS.

3,687,712 Patented Aug. 29, 1972 lUnited States Patent Office 3,687,712 WEAR RESISTANT NONWOVEN FABRIC Ludwig Hartmann, Blutenweg l,

Oberflockenbach, Germany Filed Apr. 16, 1968, Ser. No. 721,648

Claims priority, application Japan, Feb. 10, 1968,

v43/8,322 Int. Cl. C23f 17/00; D04h 3/03 U.S. Cl. 117-68 6 Claims It is known that vnon-woven fabrics can be made of staple ber of a variety of kinds. It is further known that nonwoven fabrics can be made of substantially continuous filaments.v Y .Y

.In themanufacture of nonwoven fabrics which are to 'be used as underwear or outerwear materials, the most important requirements of the fabric are good mechanical strength and .good wear resistance. Next, after these-properties, it is necessary that the fabrics possess good breathabilitiy. Experiments in themanufacture of materials for longwearing outer garments from staple bers, especially cellulosic and synthetic organic polymeric fibers, have resulted in a failure to produce satisfactory fabrics for such garments because the fabricshave been insuicient as regards their wear and strengthlcharacteristics, since such characteristics could not be satisfied by non-woven fabrics rade from short bers or staple bers. Furthermore," it has developed that nonwoven batting of v`this kind does not have adequate wrinkle resistance so that garments made from such fabrics become unsightly after a short period of wear.In 'additionVV to short ber length, a part of the difficultyhas also been attributed to the inadequate adhesion of binding substance to the finish-coated staple bers of t been in the case ofan outer garment which is subjected to considerable stress during wearing. Y

Similar difficulties have been observed with' 'a nonwoven fabric consisting of continuous bers, ysuch as one produced according to British Pat. 1,055,187, which is of continuous filaments impregnated in the usual manner with binding agents Yfor the purpose ofobtaining a stable nonwoven fabric from the relatively loose continuous lament batts. j

It is therefore an objects of this invention to provide a novel nonwoven fabric which avoids the difficulties of the prior art; f

It is another object of this invention to provide a novel method of making such novel fabric.

Other and additional objects of this 'invention will become apparent from a consideration of this entire specication, including the drawing and claims hereof.

In accordance with, and fullling these objects, one aspect of this invention resides in a novel nonwoven fabic comprising substantially continuous laments in the shape of a fabric having bonding agentimpregnatedinto said fabric predominantly at the major surfaces thereof.

The wear-resistant nonwoven fabric of this invention lhave a substantially uniform batt structure consisting of thin, continuous polymer .laments which are bonded together with about 25 to 60% and, preferably, 40 to 50% binding agent, which batts are characterized in that over 60% of all laments thereof have a titer between 0.4 and 1.2 denier, and in that the binding agent is concentrated at the surfaces of the nonwoven fabric.

The important thing is, among others, that continuous lament batts are twice impregnated, preferably with polyacrylic 'binding agents. The underwear or outerwear material thus obtained shows, not only good air and watervapor permeability, but also high tear and wear resistance.

These qualities are the consequence of the fact that, for one thing, the continuous filaments of the batt are, in contrast to batts to carde'd staple fibers, substantially free of any kind of surface nishing agents, lubricants or other such substances on the surfaces thereof.

It has developed that, in the manufacture of outerwear -types of unwoven fabrics having high wear resistance, an especially high adherence of binding agents is necessary. This especially high adherence can be achieved substantially only if lthe filaments :are free of any secondary surface-modifying substances.

vThe continuous lament batts serving as starting material for the fabric of this invention are particularly suitable for the manufacture of outerwear types of nonwoven fabrics if they are made of especially ne filaments. With uniform weight per unit 0f area and with the uniform batting achieved according to the above mentioned method of producing continuous lament battings, the fabric structure becomes increasingly dense .as the lament thickness is reduced, It is apparent that the lament fineness thus has a decisive influence on the breathability of the nonwoven fabric. If the lament diameters are too great, an excessively open structure is produced at a given weight per unit of area, giving an insufficient degree of coverage. It has been found that spun continuous lament batting produced according to the above-referred British patent are particularly well-suited for the manufacture of outerwear typesof products if their ber content consists of more than about 60% of filaments having a titer of less thanl about 1.2 denier and more than about 0.4 denier. It is not absolutely necessary for the entire amount of the bers to be within this range of titers. A small amount, e.g. about 5% of the filaments, may have a titer of less than about 0.4 denier. Furthermore, a larger percentage- -u`p to about 40--may have still coarser titers of -up to about 3 denier, if special characteristics are required. yIn order to produce such mixed filament fabrics, coarse filaments can be spun into the fabrics, as effect filaments, Without difficulty by mixed spinning, such as is described in the 'referred to British patent, by having adjacent nozzles eject different kinds of laments. These different laments :are worked into a coherent batting by oscillating the guiding ducts.

As previously mentioned, the porosity of the fabric being made has an infiuence on its subsequent properties, and the porosity is adjustable according to the titer makeup of the fibers of the non-woven batting material." In order to measure the influence of the porosity of the ber batting structure on the porosity of the end product bonded fabric, one may have recourse to the measurement of air permeability under standardized conditions (DIN 53,887). A lament batt manufactured according to the British patent from nylon 6 with an average titer of 0.8 denier, and having a weight of g./m.2, has an air permeability of 1040 l./sec./m.2 (at l0 mm. water column AP), and if the weight is 50 g./rn.2, the pe'rmeability is 1560 l./sec./m.2 under the same conditions.

-In order to use this still loose batting, consisting of continuous laments, for the manufacture of a wearresistant nonwoven fabric, the filaments must then be stances. The impregnatingv-process should beperformed cemented at their intersections. Howevenithas developed@'e--i1rsuch aemannerthatfbotlr'sidesroffthe' web-ofema-ter-i-al paring a Huid-form foam of the bonding agent, desired to be used in making the fabric of this invention; applying the iiuid foam to one major surface of the nonwoven batting; drying such impregnated foam in such manner that the binder particles tend to migrate to and concentrate atv the major surface which was impregnated with the uid foam; and repeating the Huid-foam binder impregnation and drying onY the .other major surface of the partiallyy bonded nonwoven batting.

It will be appreciated that the particles of binding agent are concentrated away from the core of theuonwoven batt and towards the two major surfaces thereof-buttllat enough binder is also in the middle of the fabric to prevent delamination. Itvshould be noted that, since the dispersed binder particles first deposit themselves along theiilament ization of the batting filamentary structure of the -nonwoven fabric subsequently obtained, which structure is permeated with capillaries.

It has been determined that concentrations of the bind ing agent in the impregnating foam-form fluid of upto a maximum of 20% are usable for the manufacture of the fabric according to the invention, with concentrations of `6% to 10% being preferred. In the case of higher im- 'pregnating liquid concentration, the wear-resistance of the nonwoven fabric diminishes rapidly. This can be explained by the fact that, after the complete impregnation of the loose batt, a migration of water towards both surfaces takes place in the drying, causing a certain amount of the binding agent particles to be thus carried towardl the surface before coagulation thereof is complete. This percent- 'addition of wetting agents stabilizes the foam-form disperf sion and promotes migration of binder particles to face.

Furthermore, the weight ratio of the binding .agent to the sur- "axes and especially at the filament intersections, the organthe filament weight is important. It has been found that the If a spun batting is impregnated with about 44% of apoly.-

acrylic dispersion described further below, the fabric has an air permeability of 940 l./sec./m.2 for a final .weight of 100 g./m.2 and an average titer of 0.8 denier; a similar fabric of 50 g./rn.2 has an air permeability of 1670 l./sec./m.2, i.e., the combined fiber and binding agent has porosities on the same order of magnitude as the plain fiber material, for comparable final weights. As already mentioned, both surfaces of the nonwoven fabric should contain a concentration of binding agent. l.

This can best be achieved by a two-step impregnation, such as set forth generally above. It is preferred that the impregnation should be carried out with certain rules being observed.

In order to obtain 4good adherence of the binding agent Y to the iilamentary structure, the filaments should be as free as possible from any kind of coatings of other subwill contain substantially equal amounts of binding agent, care being taken to see that, after the first surface has set, the other side is not too heavily loaded with the binder of the first impregnation process. Vln practice it has developedthat, in orderto achieve optimum adherence of the binding agent, the filamentsmust be substantially free of foreign. substances. If a twostepl impregnation is performed, in which first one and then the other-'side isset, traces of binding agent'from the iirst'impregnation, which might penetrate through tothe opposite side, are foreign substances insofar as the second impregnation is con'- cerned. This can be explain-remd jby the fact that these particles coagulate and crosslnk to aA certain extent during the drying processso that theyre both chemically and physically dilferent from the fresh impregnation mixture that is to be appliedlI'herefore, care must be taken4 to see that each impregnation mixture is applied to a lose, fibrous surface.. This processgcpan be performed 'particularlygwellif 'binding agents are used in the form of foarn because 'the .density and thickness of jtheffoarn permit the penetration of the fiber structure to be well-controlled'ln the'rst imf vpregnation, afoam of such a nature is applied that'it pene trates barely'beyond the center of the fiber material so that the second impregnation of the opposite side can be a'pplied to clean, so-called ..native, fibers. lIf this foamed .dispersion also has a low contents of solids, a large percenta'gel of the binding agent i particles can nii'grateftoward the surface during drying,'`and thusproducea very good wear resistance.` l 'Y A In the manufacture of nonwoven batting according' to the invention,"suitablev for use in outerwear, it' proves to be particularly desirable to-impregnate these battings made of'lowl denier polyamide filaments with polyacrylates-containing copolyinexized acrylonitrile in laddition to `a cross'- linking component, such as N-methylol acrylamdeLfThe polyacrylates must'in Vanyy case be lchemically cross-linked in order to achieve good washability andV dry-cleanability. 40

yThe 'penetrating ability ofthe impregnating foams must be adaptedto the specific wei-ghtof the iilamentarybatting. is'achieved by variations ofthe foam density; and Avariations' of the `solids Vcontent 'ofthe impregnationkmixture. It has developed that, 'for ilamentary'battings made of nylon 6, ash described above, and having the above titer compositions, the following foam adjustments are necessary; v Filamentary batt weight, g./m.2 f l :Foam Weight, g./l.

Y. If the foam .weight is varied within these -limits onthe basis of its solids content, and the solids content is from S to 20%, the peneration of the foam willtake -place in themanner that is-correct lfor the inalfsolidification.

` Understanding ofthis invention-Will -be facilitated by referenceto the accompanyingY drawing, vwhich is a schematic How diagram of theiprocess described herein..

By means of a knownfspinning apparatus, for example, lfrom British Patr. 1,055,187, a molten massof` polycaprolactarn at a temperature of 230 C. is spun into larnents 2. The spinning apparatus hasv several'- nozzles with' 160 orifices 3 having avdiameter ofv400 microns. The space between spinneret orifice amounted to 2 mm. Hot air at a temperature of 240 C; was blasted at a velocity of`200 m./sec. from the two air slits V4 running parallelfto the spnneretholes. The row of laments emerging from the ho1esafter traveling adistance of 45 rum., entered into a duct 5 togetl1er.withthe air ribbons iiowing from theair slits, while a cooling took place sothatithe'air temperature upon leaving the lbottom .end of-thc air duct amounted to onty v66" C.,at a room temperature of 40? C;

After the row Aiofilaments had been deposited ony the receiving surface 6, the diameter of the filaments wasdetermined, and the following filament-size distribution was found:

1.5% had a diameter of less than 0.4 denier 84% had a diameter between 0.41 and 1.2 denier 14.5% had a diameter between 1.2 and 1.8 denier.

Parts Polyacrylate with copolymerized acrylonitrile 96 Polyvinyl alcohol 1 Ammonoxalate 6 Silastan (wetting agent) 6 A foam of 120 g. per liter was prepared by mixing in air with an Oaks mixer.

In this foam impregnation, the roller pressure is to be adjusted so that the binding agent does not penetrate to the bottom side.

Then the batting thus impregnated is carried into a drying chamber 9 where air at 120 C. is blown onto the surface of the batting on which the foam had been applied. During the drying, a migration of the binding agent to the hotter surface takes place. In other words, a concentration of the binding agent takes place at the surface to which the foam has just been applied. If during the impregnation an amount of binding agent should have penetrated through to the bottom surface, it would largely migrate back again during the drying. In this manner the bottom side remains loose-fibered.

After leaving the dryer the web 10 of material is inverted and the impregnation process is repeated under the same conditions. The double impregnated web 11 is dried again at 120 C. and heated for another three minutes at 150 C. in a dryer 12 to thoroughly condense the binding agent.

The resulting nonwoven fabric manufactured in this manner weighed 50 g./m.2 and had good resistance to washing and dry-cleaning. Its air permeability amounted to 1650 l./sec./m.2 at 10 mm. water column AP.

What is claimed is:

1. A wear resistant nonwoven textile fabric comprising a web of varying denier substantially continuous filaments having at least about 60% of said filaments with deniers of 0.4 to 2.0 bonded together throughout at the intersections thereof with an acrylic bonding agent comprising about 25 to 60 weight percent of said fabric, which bond- 6 ing agent is concentrated at and substantially adjacent to the two major surfaces thereof, and is also present in the middle of the fabric to an extent sufiicient to prevent delamination of said fabric.

2. Fabric as claimed in claim 1, wherein said bonding agent comprises about 40 to 50 weight percent thereof.

3. Fabric as claimed in claim 1, wherein said bonding agent is a cross-linked polymer of acrylonitrile, n-butylacrylate and N-methylolacrylamide.

4. Fabric claimed in claim 1, wherein said filaments are polyamide.

5. Fabric as claimed in claim 1, wherein said filament size distribution is up to about 5% less than about 0.4 denier; up to about 40% about 1.2 to 3 denier; and the remainder about 0.4 to 1.2 denier.

6. Process of producing a nonwoven fabric as claimed in claim 1, comprising; preparing a non-woven web of thermoplastic substantially continuous filaments; preparing a Huid-foam impregnant composition comprising an aqueous dispersion of an acrylic resin having a solids content of up to about 20 weight percent; coating said uid foam onto a first major surface of said non-woven web and impregnating such foam into said web; heating said coated and impregnated web to a temperature and for a time sufficient to substantially remove the liquid portion of the impregnant, to cause said resin to migrate toward said heat and to deposit said resin substantially at and adjacent to said first major surface; coating the second major surface of said nonwoven web with a second aliquot of said fiuid foam and impregnating such foam into said web; and heating said second coated and impregnated web to a temperature and for a time suicient to substantially remove the liquid portion of the impregnant, to cause said resin to migrate toward said heat and to deposit said resin substantially at and adjacent to said second major surface while retaining enough bonding agent in the middle of the fabric to prevent delamination thereof.

References Cited UNITED STATES PATENTS 3,030,232 4/ 1962 Morgenstern 117-68 X 3,323,959 6/1967 Kreckl 117-140 A 3,471,315 10/1969 Be et al. 161-164 X 2,972,554 2/ 1961 Muskat et al 161-157 X 3,274,046 9/ 1966 Shannon et al. 161-157 X FOREIGN PATENTS 1,055,187 1/ 1967 Great Britain.

ROBERT F. BURNETI, Primary Examiner R. L. MAY, Assistant Examiner U.S. C1. X.R.

117-140 A, 161 UN; 156-167, 181; 161-140, 164 

